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src/Source/LibPNG/pngrtran.c  view on Meta::CPAN

/* Modify the info structure to reflect the transformations.  The
 * info should be updated so a PNG file could be written with it,
 * assuming the transformations result in valid PNG data.
 */
void /* PRIVATE */
png_read_transform_info(png_structrp png_ptr, png_inforp info_ptr)
{
   png_debug(1, "in png_read_transform_info");

#ifdef PNG_READ_EXPAND_SUPPORTED
   if ((png_ptr->transformations & PNG_EXPAND) != 0)
   {
      if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      {
         /* This check must match what actually happens in
          * png_do_expand_palette; if it ever checks the tRNS chunk to see if
          * it is all opaque we must do the same (at present it does not.)
          */
         if (png_ptr->num_trans > 0)
            info_ptr->color_type = PNG_COLOR_TYPE_RGB_ALPHA;

         else
            info_ptr->color_type = PNG_COLOR_TYPE_RGB;

         info_ptr->bit_depth = 8;
         info_ptr->num_trans = 0;

         if (png_ptr->palette == NULL)
            png_error (png_ptr, "Palette is NULL in indexed image");
      }
      else
      {
         if (png_ptr->num_trans != 0)
         {
            if ((png_ptr->transformations & PNG_EXPAND_tRNS) != 0)
               info_ptr->color_type |= PNG_COLOR_MASK_ALPHA;
         }
         if (info_ptr->bit_depth < 8)
            info_ptr->bit_depth = 8;

         info_ptr->num_trans = 0;
      }
   }
#endif

#if defined(PNG_READ_BACKGROUND_SUPPORTED) ||\
   defined(PNG_READ_ALPHA_MODE_SUPPORTED)
   /* The following is almost certainly wrong unless the background value is in
    * the screen space!
    */
   if ((png_ptr->transformations & PNG_COMPOSE) != 0)
      info_ptr->background = png_ptr->background;
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
   /* The following used to be conditional on PNG_GAMMA (prior to 1.5.4),
    * however it seems that the code in png_init_read_transformations, which has
    * been called before this from png_read_update_info->png_read_start_row
    * sometimes does the gamma transform and cancels the flag.
    *
    * TODO: this looks wrong; the info_ptr should end up with a gamma equal to
    * the screen_gamma value.  The following probably results in weirdness if
    * the info_ptr is used by the app after the rows have been read.
    */
   info_ptr->colorspace.gamma = png_ptr->colorspace.gamma;
#endif

   if (info_ptr->bit_depth == 16)
   {
#  ifdef PNG_READ_16BIT_SUPPORTED
#     ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
         if ((png_ptr->transformations & PNG_SCALE_16_TO_8) != 0)
            info_ptr->bit_depth = 8;
#     endif

#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
         if ((png_ptr->transformations & PNG_16_TO_8) != 0)
            info_ptr->bit_depth = 8;
#     endif

#  else
      /* No 16 bit support: force chopping 16-bit input down to 8, in this case
       * the app program can chose if both APIs are available by setting the
       * correct scaling to use.
       */
#     ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
         /* For compatibility with previous versions use the strip method by
          * default.  This code works because if PNG_SCALE_16_TO_8 is already
          * set the code below will do that in preference to the chop.
          */
         png_ptr->transformations |= PNG_16_TO_8;
         info_ptr->bit_depth = 8;
#     else

#        ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
            png_ptr->transformations |= PNG_SCALE_16_TO_8;
            info_ptr->bit_depth = 8;
#        else

            CONFIGURATION ERROR: you must enable at least one 16 to 8 method
#        endif
#    endif
#endif /* !READ_16BIT */
   }

#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
   if ((png_ptr->transformations & PNG_GRAY_TO_RGB) != 0)
      info_ptr->color_type = (png_byte)(info_ptr->color_type |
         PNG_COLOR_MASK_COLOR);
#endif

#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
   if ((png_ptr->transformations & PNG_RGB_TO_GRAY) != 0)
      info_ptr->color_type = (png_byte)(info_ptr->color_type &
         ~PNG_COLOR_MASK_COLOR);
#endif

#ifdef PNG_READ_QUANTIZE_SUPPORTED
   if ((png_ptr->transformations & PNG_QUANTIZE) != 0)
   {
      if (((info_ptr->color_type == PNG_COLOR_TYPE_RGB) ||

src/Source/LibPNG/pngrtran.c  view on Meta::CPAN

      }
   }
}
#endif

#ifdef PNG_READ_EXPAND_16_SUPPORTED
/* If the bit depth is 8 and the color type is not a palette type expand the
 * whole row to 16 bits.  Has no effect otherwise.
 */
static void
png_do_expand_16(png_row_infop row_info, png_bytep row)
{
   if (row_info->bit_depth == 8 &&
      row_info->color_type != PNG_COLOR_TYPE_PALETTE)
   {
      /* The row have a sequence of bytes containing [0..255] and we need
       * to turn it into another row containing [0..65535], to do this we
       * calculate:
       *
       *  (input / 255) * 65535
       *
       *  Which happens to be exactly input * 257 and this can be achieved
       *  simply by byte replication in place (copying backwards).
       */
      png_byte *sp = row + row_info->rowbytes; /* source, last byte + 1 */
      png_byte *dp = sp + row_info->rowbytes;  /* destination, end + 1 */
      while (dp > sp)
         dp[-2] = dp[-1] = *--sp, dp -= 2;

      row_info->rowbytes *= 2;
      row_info->bit_depth = 16;
      row_info->pixel_depth = (png_byte)(row_info->channels * 16);
   }
}
#endif

#ifdef PNG_READ_QUANTIZE_SUPPORTED
static void
png_do_quantize(png_row_infop row_info, png_bytep row,
    png_const_bytep palette_lookup, png_const_bytep quantize_lookup)
{
   png_bytep sp, dp;
   png_uint_32 i;
   png_uint_32 row_width=row_info->width;

   png_debug(1, "in png_do_quantize");

   if (row_info->bit_depth == 8)
   {
      if (row_info->color_type == PNG_COLOR_TYPE_RGB && palette_lookup)
      {
         int r, g, b, p;
         sp = row;
         dp = row;
         for (i = 0; i < row_width; i++)
         {
            r = *sp++;
            g = *sp++;
            b = *sp++;

            /* This looks real messy, but the compiler will reduce
             * it down to a reasonable formula.  For example, with
             * 5 bits per color, we get:
             * p = (((r >> 3) & 0x1f) << 10) |
             *    (((g >> 3) & 0x1f) << 5) |
             *    ((b >> 3) & 0x1f);
             */
            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                (PNG_QUANTIZE_BLUE_BITS)) |
                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

            *dp++ = palette_lookup[p];
         }

         row_info->color_type = PNG_COLOR_TYPE_PALETTE;
         row_info->channels = 1;
         row_info->pixel_depth = row_info->bit_depth;
         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
      }

      else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA &&
         palette_lookup != NULL)
      {
         int r, g, b, p;
         sp = row;
         dp = row;
         for (i = 0; i < row_width; i++)
         {
            r = *sp++;
            g = *sp++;
            b = *sp++;
            sp++;

            p = (((r >> (8 - PNG_QUANTIZE_RED_BITS)) &
                ((1 << PNG_QUANTIZE_RED_BITS) - 1)) <<
                (PNG_QUANTIZE_GREEN_BITS + PNG_QUANTIZE_BLUE_BITS)) |
                (((g >> (8 - PNG_QUANTIZE_GREEN_BITS)) &
                ((1 << PNG_QUANTIZE_GREEN_BITS) - 1)) <<
                (PNG_QUANTIZE_BLUE_BITS)) |
                ((b >> (8 - PNG_QUANTIZE_BLUE_BITS)) &
                ((1 << PNG_QUANTIZE_BLUE_BITS) - 1));

            *dp++ = palette_lookup[p];
         }

         row_info->color_type = PNG_COLOR_TYPE_PALETTE;
         row_info->channels = 1;
         row_info->pixel_depth = row_info->bit_depth;
         row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth, row_width);
      }

      else if (row_info->color_type == PNG_COLOR_TYPE_PALETTE &&
         quantize_lookup)
      {
         sp = row;